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synapse-product/synapse/events/spamcheck.py
David Teller a164a46038
Uniformize spam-checker API, part 4: port other spam-checker callbacks to return Union[Allow, Codes]. (#12857) 
Co-authored-by: Brendan Abolivier <babolivier@matrix.org>
2022-06-13 18:16:16 +00:00

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# Copyright 2017 New Vector Ltd
# Copyright 2019 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import inspect
import logging
from typing import (
TYPE_CHECKING,
Any,
Awaitable,
Callable,
Collection,
Dict,
List,
Optional,
Tuple,
Union,
)
# `Literal` appears with Python 3.8.
from typing_extensions import Literal
import synapse
from synapse.rest.media.v1._base import FileInfo
from synapse.rest.media.v1.media_storage import ReadableFileWrapper
from synapse.spam_checker_api import RegistrationBehaviour
from synapse.types import RoomAlias, UserProfile
from synapse.util.async_helpers import delay_cancellation, maybe_awaitable
from synapse.util.metrics import Measure
if TYPE_CHECKING:
import synapse.events
import synapse.server
logger = logging.getLogger(__name__)
CHECK_EVENT_FOR_SPAM_CALLBACK = Callable[
["synapse.events.EventBase"],
Awaitable[
Union[
str,
"synapse.api.errors.Codes",
# Highly experimental, not officially part of the spamchecker API, may
# disappear without warning depending on the results of ongoing
# experiments.
# Use this to return additional information as part of an error.
Tuple["synapse.api.errors.Codes", Dict],
# Deprecated
bool,
]
],
]
SHOULD_DROP_FEDERATED_EVENT_CALLBACK = Callable[
["synapse.events.EventBase"],
Awaitable[Union[bool, str]],
]
USER_MAY_JOIN_ROOM_CALLBACK = Callable[
[str, str, bool],
Awaitable[
Union[
Literal["NOT_SPAM"],
"synapse.api.errors.Codes",
# Deprecated
bool,
]
],
]
USER_MAY_INVITE_CALLBACK = Callable[
[str, str, str],
Awaitable[
Union[
Literal["NOT_SPAM"],
"synapse.api.errors.Codes",
# Deprecated
bool,
]
],
]
USER_MAY_SEND_3PID_INVITE_CALLBACK = Callable[
[str, str, str, str],
Awaitable[
Union[
Literal["NOT_SPAM"],
"synapse.api.errors.Codes",
# Deprecated
bool,
]
],
]
USER_MAY_CREATE_ROOM_CALLBACK = Callable[
[str],
Awaitable[
Union[
Literal["NOT_SPAM"],
"synapse.api.errors.Codes",
# Deprecated
bool,
]
],
]
USER_MAY_CREATE_ROOM_ALIAS_CALLBACK = Callable[
[str, RoomAlias],
Awaitable[
Union[
Literal["NOT_SPAM"],
"synapse.api.errors.Codes",
# Deprecated
bool,
]
],
]
USER_MAY_PUBLISH_ROOM_CALLBACK = Callable[
[str, str],
Awaitable[
Union[
Literal["NOT_SPAM"],
"synapse.api.errors.Codes",
# Deprecated
bool,
]
],
]
CHECK_USERNAME_FOR_SPAM_CALLBACK = Callable[[UserProfile], Awaitable[bool]]
LEGACY_CHECK_REGISTRATION_FOR_SPAM_CALLBACK = Callable[
[
Optional[dict],
Optional[str],
Collection[Tuple[str, str]],
],
Awaitable[RegistrationBehaviour],
]
CHECK_REGISTRATION_FOR_SPAM_CALLBACK = Callable[
[
Optional[dict],
Optional[str],
Collection[Tuple[str, str]],
Optional[str],
],
Awaitable[RegistrationBehaviour],
]
CHECK_MEDIA_FILE_FOR_SPAM_CALLBACK = Callable[
[ReadableFileWrapper, FileInfo],
Awaitable[
Union[
Literal["NOT_SPAM"],
"synapse.api.errors.Codes",
# Deprecated
bool,
]
],
]
def load_legacy_spam_checkers(hs: "synapse.server.HomeServer") -> None:
"""Wrapper that loads spam checkers configured using the old configuration, and
registers the spam checker hooks they implement.
"""
spam_checkers: List[Any] = []
api = hs.get_module_api()
for module, config in hs.config.spamchecker.spam_checkers:
# Older spam checkers don't accept the `api` argument, so we
# try and detect support.
spam_args = inspect.getfullargspec(module)
if "api" in spam_args.args:
spam_checkers.append(module(config=config, api=api))
else:
spam_checkers.append(module(config=config))
# The known spam checker hooks. If a spam checker module implements a method
# which name appears in this set, we'll want to register it.
spam_checker_methods = {
"check_event_for_spam",
"user_may_invite",
"user_may_create_room",
"user_may_create_room_alias",
"user_may_publish_room",
"check_username_for_spam",
"check_registration_for_spam",
"check_media_file_for_spam",
}
for spam_checker in spam_checkers:
# Methods on legacy spam checkers might not be async, so we wrap them around a
# wrapper that will call maybe_awaitable on the result.
def async_wrapper(f: Optional[Callable]) -> Optional[Callable[..., Awaitable]]:
# f might be None if the callback isn't implemented by the module. In this
# case we don't want to register a callback at all so we return None.
if f is None:
return None
wrapped_func = f
if f.__name__ == "check_registration_for_spam":
checker_args = inspect.signature(f)
if len(checker_args.parameters) == 3:
# Backwards compatibility; some modules might implement a hook that
# doesn't expect a 4th argument. In this case, wrap it in a function
# that gives it only 3 arguments and drops the auth_provider_id on
# the floor.
def wrapper(
email_threepid: Optional[dict],
username: Optional[str],
request_info: Collection[Tuple[str, str]],
auth_provider_id: Optional[str],
) -> Union[Awaitable[RegistrationBehaviour], RegistrationBehaviour]:
# Assertion required because mypy can't prove we won't
# change `f` back to `None`. See
# https://mypy.readthedocs.io/en/latest/common_issues.html#narrowing-and-inner-functions
assert f is not None
return f(
email_threepid,
username,
request_info,
)
wrapped_func = wrapper
elif len(checker_args.parameters) != 4:
raise RuntimeError(
"Bad signature for callback check_registration_for_spam",
)
def run(*args: Any, **kwargs: Any) -> Awaitable:
# Assertion required because mypy can't prove we won't change `f`
# back to `None`. See
# https://mypy.readthedocs.io/en/latest/common_issues.html#narrowing-and-inner-functions
assert wrapped_func is not None
return maybe_awaitable(wrapped_func(*args, **kwargs))
return run
# Register the hooks through the module API.
hooks = {
hook: async_wrapper(getattr(spam_checker, hook, None))
for hook in spam_checker_methods
}
api.register_spam_checker_callbacks(**hooks)
class SpamChecker:
NOT_SPAM: Literal["NOT_SPAM"] = "NOT_SPAM"
def __init__(self, hs: "synapse.server.HomeServer") -> None:
self.hs = hs
self.clock = hs.get_clock()
self._check_event_for_spam_callbacks: List[CHECK_EVENT_FOR_SPAM_CALLBACK] = []
self._should_drop_federated_event_callbacks: List[
SHOULD_DROP_FEDERATED_EVENT_CALLBACK
] = []
self._user_may_join_room_callbacks: List[USER_MAY_JOIN_ROOM_CALLBACK] = []
self._user_may_invite_callbacks: List[USER_MAY_INVITE_CALLBACK] = []
self._user_may_send_3pid_invite_callbacks: List[
USER_MAY_SEND_3PID_INVITE_CALLBACK
] = []
self._user_may_create_room_callbacks: List[USER_MAY_CREATE_ROOM_CALLBACK] = []
self._user_may_create_room_alias_callbacks: List[
USER_MAY_CREATE_ROOM_ALIAS_CALLBACK
] = []
self._user_may_publish_room_callbacks: List[USER_MAY_PUBLISH_ROOM_CALLBACK] = []
self._check_username_for_spam_callbacks: List[
CHECK_USERNAME_FOR_SPAM_CALLBACK
] = []
self._check_registration_for_spam_callbacks: List[
CHECK_REGISTRATION_FOR_SPAM_CALLBACK
] = []
self._check_media_file_for_spam_callbacks: List[
CHECK_MEDIA_FILE_FOR_SPAM_CALLBACK
] = []
def register_callbacks(
self,
check_event_for_spam: Optional[CHECK_EVENT_FOR_SPAM_CALLBACK] = None,
should_drop_federated_event: Optional[
SHOULD_DROP_FEDERATED_EVENT_CALLBACK
] = None,
user_may_join_room: Optional[USER_MAY_JOIN_ROOM_CALLBACK] = None,
user_may_invite: Optional[USER_MAY_INVITE_CALLBACK] = None,
user_may_send_3pid_invite: Optional[USER_MAY_SEND_3PID_INVITE_CALLBACK] = None,
user_may_create_room: Optional[USER_MAY_CREATE_ROOM_CALLBACK] = None,
user_may_create_room_alias: Optional[
USER_MAY_CREATE_ROOM_ALIAS_CALLBACK
] = None,
user_may_publish_room: Optional[USER_MAY_PUBLISH_ROOM_CALLBACK] = None,
check_username_for_spam: Optional[CHECK_USERNAME_FOR_SPAM_CALLBACK] = None,
check_registration_for_spam: Optional[
CHECK_REGISTRATION_FOR_SPAM_CALLBACK
] = None,
check_media_file_for_spam: Optional[CHECK_MEDIA_FILE_FOR_SPAM_CALLBACK] = None,
) -> None:
"""Register callbacks from module for each hook."""
if check_event_for_spam is not None:
self._check_event_for_spam_callbacks.append(check_event_for_spam)
if should_drop_federated_event is not None:
self._should_drop_federated_event_callbacks.append(
should_drop_federated_event
)
if user_may_join_room is not None:
self._user_may_join_room_callbacks.append(user_may_join_room)
if user_may_invite is not None:
self._user_may_invite_callbacks.append(user_may_invite)
if user_may_send_3pid_invite is not None:
self._user_may_send_3pid_invite_callbacks.append(
user_may_send_3pid_invite,
)
if user_may_create_room is not None:
self._user_may_create_room_callbacks.append(user_may_create_room)
if user_may_create_room_alias is not None:
self._user_may_create_room_alias_callbacks.append(
user_may_create_room_alias,
)
if user_may_publish_room is not None:
self._user_may_publish_room_callbacks.append(user_may_publish_room)
if check_username_for_spam is not None:
self._check_username_for_spam_callbacks.append(check_username_for_spam)
if check_registration_for_spam is not None:
self._check_registration_for_spam_callbacks.append(
check_registration_for_spam,
)
if check_media_file_for_spam is not None:
self._check_media_file_for_spam_callbacks.append(check_media_file_for_spam)
async def check_event_for_spam(
self, event: "synapse.events.EventBase"
) -> Union[Tuple["synapse.api.errors.Codes", Dict], str]:
"""Checks if a given event is considered "spammy" by this server.
If the server considers an event spammy, then it will be rejected if
sent by a local user. If it is sent by a user on another server, the
event is soft-failed.
Args:
event: the event to be checked
Returns:
- `NOT_SPAM` if the event is considered good (non-spammy) and should be let
through. Other spamcheck filters may still reject it.
- A `Code` if the event is considered spammy and is rejected with a specific
error message/code.
- A string that isn't `NOT_SPAM` if the event is considered spammy and the
string should be used as the client-facing error message. This usage is
generally discouraged as it doesn't support internationalization.
"""
for callback in self._check_event_for_spam_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
res = await delay_cancellation(callback(event))
if res is False or res == self.NOT_SPAM:
# This spam-checker accepts the event.
# Other spam-checkers may reject it, though.
continue
elif res is True:
# This spam-checker rejects the event with deprecated
# return value `True`
return (synapse.api.errors.Codes.FORBIDDEN, {})
elif not isinstance(res, str):
# mypy complains that we can't reach this code because of the
# return type in CHECK_EVENT_FOR_SPAM_CALLBACK, but we don't know
# for sure that the module actually returns it.
logger.warning(
"Module returned invalid value, rejecting message as spam"
)
res = "This message has been rejected as probable spam"
else:
# The module rejected the event either with a `Codes`
# or some other `str`. In either case, we stop here.
pass
return res
# No spam-checker has rejected the event, let it pass.
return self.NOT_SPAM
async def should_drop_federated_event(
self, event: "synapse.events.EventBase"
) -> Union[bool, str]:
"""Checks if a given federated event is considered "spammy" by this
server.
If the server considers an event spammy, it will be silently dropped,
and in doing so will split-brain our view of the room's DAG.
Args:
event: the event to be checked
Returns:
True if the event should be silently dropped
"""
for callback in self._should_drop_federated_event_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
res: Union[bool, str] = await delay_cancellation(callback(event))
if res:
return res
return False
async def user_may_join_room(
self, user_id: str, room_id: str, is_invited: bool
) -> Union["synapse.api.errors.Codes", Literal["NOT_SPAM"]]:
"""Checks if a given users is allowed to join a room.
Not called when a user creates a room.
Args:
userid: The ID of the user wanting to join the room
room_id: The ID of the room the user wants to join
is_invited: Whether the user is invited into the room
Returns:
NOT_SPAM if the operation is permitted, Codes otherwise.
"""
for callback in self._user_may_join_room_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
res = await delay_cancellation(callback(user_id, room_id, is_invited))
# Normalize return values to `Codes` or `"NOT_SPAM"`.
if res is True or res is self.NOT_SPAM:
continue
elif res is False:
return synapse.api.errors.Codes.FORBIDDEN
elif isinstance(res, synapse.api.errors.Codes):
return res
else:
logger.warning(
"Module returned invalid value, rejecting join as spam"
)
return synapse.api.errors.Codes.FORBIDDEN
# No spam-checker has rejected the request, let it pass.
return self.NOT_SPAM
async def user_may_invite(
self, inviter_userid: str, invitee_userid: str, room_id: str
) -> Union["synapse.api.errors.Codes", Literal["NOT_SPAM"]]:
"""Checks if a given user may send an invite
Args:
inviter_userid: The user ID of the sender of the invitation
invitee_userid: The user ID targeted in the invitation
room_id: The room ID
Returns:
NOT_SPAM if the operation is permitted, Codes otherwise.
"""
for callback in self._user_may_invite_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
res = await delay_cancellation(
callback(inviter_userid, invitee_userid, room_id)
)
# Normalize return values to `Codes` or `"NOT_SPAM"`.
if res is True or res is self.NOT_SPAM:
continue
elif res is False:
return synapse.api.errors.Codes.FORBIDDEN
elif isinstance(res, synapse.api.errors.Codes):
return res
else:
logger.warning(
"Module returned invalid value, rejecting invite as spam"
)
return synapse.api.errors.Codes.FORBIDDEN
# No spam-checker has rejected the request, let it pass.
return self.NOT_SPAM
async def user_may_send_3pid_invite(
self, inviter_userid: str, medium: str, address: str, room_id: str
) -> Union["synapse.api.errors.Codes", Literal["NOT_SPAM"]]:
"""Checks if a given user may invite a given threepid into the room
Note that if the threepid is already associated with a Matrix user ID, Synapse
will call user_may_invite with said user ID instead.
Args:
inviter_userid: The user ID of the sender of the invitation
medium: The 3PID's medium (e.g. "email")
address: The 3PID's address (e.g. "alice@example.com")
room_id: The room ID
Returns:
NOT_SPAM if the operation is permitted, Codes otherwise.
"""
for callback in self._user_may_send_3pid_invite_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
res = await delay_cancellation(
callback(inviter_userid, medium, address, room_id)
)
# Normalize return values to `Codes` or `"NOT_SPAM"`.
if res is True or res is self.NOT_SPAM:
continue
elif res is False:
return synapse.api.errors.Codes.FORBIDDEN
elif isinstance(res, synapse.api.errors.Codes):
return res
else:
logger.warning(
"Module returned invalid value, rejecting 3pid invite as spam"
)
return synapse.api.errors.Codes.FORBIDDEN
return self.NOT_SPAM
async def user_may_create_room(
self, userid: str
) -> Union["synapse.api.errors.Codes", Literal["NOT_SPAM"]]:
"""Checks if a given user may create a room
Args:
userid: The ID of the user attempting to create a room
"""
for callback in self._user_may_create_room_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
res = await delay_cancellation(callback(userid))
if res is True or res is self.NOT_SPAM:
continue
elif res is False:
return synapse.api.errors.Codes.FORBIDDEN
elif isinstance(res, synapse.api.errors.Codes):
return res
else:
logger.warning(
"Module returned invalid value, rejecting room creation as spam"
)
return synapse.api.errors.Codes.FORBIDDEN
return self.NOT_SPAM
async def user_may_create_room_alias(
self, userid: str, room_alias: RoomAlias
) -> Union["synapse.api.errors.Codes", Literal["NOT_SPAM"]]:
"""Checks if a given user may create a room alias
Args:
userid: The ID of the user attempting to create a room alias
room_alias: The alias to be created
"""
for callback in self._user_may_create_room_alias_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
res = await delay_cancellation(callback(userid, room_alias))
if res is True or res is self.NOT_SPAM:
continue
elif res is False:
return synapse.api.errors.Codes.FORBIDDEN
elif isinstance(res, synapse.api.errors.Codes):
return res
else:
logger.warning(
"Module returned invalid value, rejecting room create as spam"
)
return synapse.api.errors.Codes.FORBIDDEN
return self.NOT_SPAM
async def user_may_publish_room(
self, userid: str, room_id: str
) -> Union["synapse.api.errors.Codes", Literal["NOT_SPAM"]]:
"""Checks if a given user may publish a room to the directory
Args:
userid: The user ID attempting to publish the room
room_id: The ID of the room that would be published
"""
for callback in self._user_may_publish_room_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
res = await delay_cancellation(callback(userid, room_id))
if res is True or res is self.NOT_SPAM:
continue
elif res is False:
return synapse.api.errors.Codes.FORBIDDEN
elif isinstance(res, synapse.api.errors.Codes):
return res
else:
logger.warning(
"Module returned invalid value, rejecting room publication as spam"
)
return synapse.api.errors.Codes.FORBIDDEN
return self.NOT_SPAM
async def check_username_for_spam(self, user_profile: UserProfile) -> bool:
"""Checks if a user ID or display name are considered "spammy" by this server.
If the server considers a username spammy, then it will not be included in
user directory results.
Args:
user_profile: The user information to check, it contains the keys:
* user_id
* display_name
* avatar_url
Returns:
True if the user is spammy.
"""
for callback in self._check_username_for_spam_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
# Make a copy of the user profile object to ensure the spam checker cannot
# modify it.
res = await delay_cancellation(callback(user_profile.copy()))
if res:
return True
return False
async def check_registration_for_spam(
self,
email_threepid: Optional[dict],
username: Optional[str],
request_info: Collection[Tuple[str, str]],
auth_provider_id: Optional[str] = None,
) -> RegistrationBehaviour:
"""Checks if we should allow the given registration request.
Args:
email_threepid: The email threepid used for registering, if any
username: The request user name, if any
request_info: List of tuples of user agent and IP that
were used during the registration process.
auth_provider_id: The SSO IdP the user used, e.g "oidc", "saml",
"cas". If any. Note this does not include users registered
via a password provider.
Returns:
Enum for how the request should be handled
"""
for callback in self._check_registration_for_spam_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
behaviour = await delay_cancellation(
callback(email_threepid, username, request_info, auth_provider_id)
)
assert isinstance(behaviour, RegistrationBehaviour)
if behaviour != RegistrationBehaviour.ALLOW:
return behaviour
return RegistrationBehaviour.ALLOW
async def check_media_file_for_spam(
self, file_wrapper: ReadableFileWrapper, file_info: FileInfo
) -> Union["synapse.api.errors.Codes", Literal["NOT_SPAM"]]:
"""Checks if a piece of newly uploaded media should be blocked.
This will be called for local uploads, downloads of remote media, each
thumbnail generated for those, and web pages/images used for URL
previews.
Note that care should be taken to not do blocking IO operations in the
main thread. For example, to get the contents of a file a module
should do::
async def check_media_file_for_spam(
self, file: ReadableFileWrapper, file_info: FileInfo
) -> Union[Codes, Literal["NOT_SPAM"]]:
buffer = BytesIO()
await file.write_chunks_to(buffer.write)
if buffer.getvalue() == b"Hello World":
return synapse.module_api.NOT_SPAM
return Codes.FORBIDDEN
Args:
file: An object that allows reading the contents of the media.
file_info: Metadata about the file.
"""
for callback in self._check_media_file_for_spam_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
res = await delay_cancellation(callback(file_wrapper, file_info))
# Normalize return values to `Codes` or `"NOT_SPAM"`.
if res is False or res is self.NOT_SPAM:
continue
elif res is True:
return synapse.api.errors.Codes.FORBIDDEN
elif isinstance(res, synapse.api.errors.Codes):
return res
else:
logger.warning(
"Module returned invalid value, rejecting media file as spam"
)
return synapse.api.errors.Codes.FORBIDDEN
return self.NOT_SPAM
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